Fluid power device



Jan. 2, 1951 F. BERRY FLUID POWER DEVICE 4 Sheets-Sheet 1 Filed April 27, 1945 Jan. 2, 1951 F. BERRY FLUID POWER DEVICE 4 Sheets-Shea?l 2 Filed April 27, 1945 INVENTOR. EMA/ BER/w rra/iwf? Sv QN Nm, Mm. bv mw.

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FLUID POWER DEVICE Filed April 27, 1945 4 Sheets-Sheet 4 Vf R 9,. E mm E mw m m n m E. M E m /m/ /7 ,V 7 NN W. M W l mw m A f w Y Il mm wh Q @N xu Patented Jan. 2, 1951 FLUID POWER DEVICE Frank Berry, Corinth, Miss., assigner to Berry Motors, Inc., Corinth, Miss., a corporation of Tennessee Application April 27, 1945, Serial No. 590,543

10 Claims. l

This invention relates to hydraulic power devices, such as hydraulic pumps, hydraulic motors `and servo-motors, hydraulic transmissions, power connecters and controls therefor.

One of the objects of the invention is to provide a hydraulic pump or transmission which will deliver' a variable Volume of fluid under variable pressure to a hydraulic motor to drive it at variable speed under varying loads. A hydraulic pump of these characteristics, together with the driven hydraulic motor making up the transmission unit, would nd special application under circumstances, such as in machine tools, where the power supply is constant and the load varies. Another application would be hydraulic transmissions for automobiles where the unit would be further provided with manual control means. The pump would be useful to furnish a variable volume under a constant pressure, as for examples, fuel supply pumps, injectors and the like.

For the attainment of the foregoing and such other objects of invention as may appear or be pointed out herein I have shown several embodiments of my invention. in the accompanying drawings, wherein- Figure 1 is4 a longitudinal section through a form of multiple cylinder pump in which. the cylinders are arranged in parallel and in communication with a common manifold which forms. part of a control device for varying the volume delivered to the driven motor of theV transmission unit to accommodate varying load conditions;

Figure 2 is a transverse section through one of the cylinders taken on the line 2--2 of Figure 1;

Figure 3 is a perspective view of the piston valve forming part of the control device of the pump unit of Figure 1;

Figure 4 is a perspective view of the pump and control device of Figure 1 with. the upper half of the end and the front of the casing removed to expose the interior of both the pump and the control valve.; 1

Figure 5 isy a perspective view similar to Figure 4 showing a hydraulicY motor implemented with a variable speed device;

Figure 6 is a. vertical longitudinal section, on the line 6 6', Figure 7, through a modified form of the device, adapted for use as a double stage variable speed hydraulic transmission;

Figure 7, is a transverse section taken on the line` I-'I', Figure 6;

Figure 8 is a longitudinal section on line `8---8 of Fig. 7 through an automatic uid porting, device adapted to control the admission of fluid to (Cl. 10S- 120) 2 the cylinders, similar to those illustrated in Figures 1 and 4.

Figure 9 is a perspective view showing the relative positions of the pistons on the drive shaft.

In Figuresl l to 4 inclusive is shown an embodiment of my invention which has pressure, volume and torque controls.

Referring especially to Figures i to 4, it will be seen that the rotary elements are contained within an outer casing I. The interior` portion of the casing is provided with a long circular bore within which is rotatively mounted a cylindrical abutment rotor 3.

Secured to the outer casing I, as by means, of bolts BX, Figure 1 and extending radially inwardly are three annularly shaped members 9 which separate the interior of outer casing I into four annular cylinders designated from left to right in Figure l as II, IIX, IIXX, and IIXXX. Cylinder separators 9 are of irregular cross-section, see Figure 1, having oppostely facing portions between which 4are disposed the piston rotors I0, IIIX, I0, and. IIiXXX, respectively. Also, the Ieft housing wall 'I has a rightwardly facing portion between which and the leftwardly facing portion of separator 9 is disposed the left piston rotor I0; similarly, the right housing wall IXX has a leftwardly facing portion between which and the rightwardly facing portion of separator 9 is disposed the right piston rotor IIlXXX.V The central piston rotors Iiix and HJXX are disposed between the oppositely facing portions of three of the separators 9. The piston rotors II), etc., are secured, as by keys IE,V to a drive shaft I2 rotatively -mounted in anti-friction bearings I8. The right end of drive shaft I2 is provided with a reduced portion I2 and provided with the inner yace of an anti-friction. bearing I8.

Pistons i3, I3X, i3, and IXXX, which` are slidably received in the annular cylinders, respectively II, IIX, and IIXX- and IIXXX, are fastened to their rotors, respectively, i9, IIlX, and meX and IBXXX by bolts I4.

Piston drive shaft I2 rotates in synchronism with abutment rotor 3 which is common to all four pistons. For this purpose spur gear IEX, Figure l, is secured, as by key I tx, to the left spindle 3X of abutment rotor 3, and meshes with a gear I5 secured, as by key ISXX, on drive shaft I2. The spindles of the abutment rotor are mounted on anti-friction bearings I9.

The common abutment rotor 3 is provided with four arcuate cut-outs 3a, each of which provides a` space in which a respective one of the four pistons i3, I3", i3, ISXXX clears.

inder 43, see Figure 1, is a second cylinder 43X of somewhat greater diameter, the two cylinders being separated by a wall 26. Within the smaller cylinder 43 is a piston 4| secured at the left end of a rod 4S which slides in an appropriate hole provided for it in the wall 25. At the right end of piston rod 43 is a second piston 25 which slides in the larger cylinder 43X. A long helical spring encircles piston rod 4D within the smaller cylinder 43 between left piston 4I and separating wall 2d. The wall 23 is provided with a number of small holes 23a for the purpose of restricting the huid now between cylinder 43 to cylinder 43X, the object being to prevent spasmodic movement of the piston assembly. A cover plate 2'1 with bleeder hole 2S is fastened by bolts 3d at the right end of cylinder 43X.

A detail of the smaller piston 4| is shown in l VFigure 3 where it will be seen that the frame constitutes a skeleton piston with openings 33 which are in communication with an annular opening 34 at the piston rod end of the piston. Slidably mounted on piston rod 4t is a disc 3i which serves as a valve to close the annular opening 34, a coil spring 32 being provided to urge disc 3i to closing position.

The strength of coil spring 28 is such that under no-load or idling conditions the piston 4l is held by the spring in its leftmost position shown in Figure l with the piston entirely clear of by-pass outlet 44. The fluid, which is fed to the unit through common inlet or manifold 4t and via the passages 4i to the different annular cylinders l, itx, lilXX, and IiXXX, is forced by the pistons i3, l3x, ISXX, and ISXXX thereof through the individual ducts 42, 42X, 42, and l2-Xx leading from the respective cylinders into the common cylinder 43. From common cylinder i3 the fluid is forced, through the un-bldcked by-pass outlet 44 to a storage tank or accumulator (not shown) which has a return leg to the inlet 45. Within this fluid circuit through the annular cylinders of the pump, their individual ducts 42, etc., common cylinder 43, by-pass outlet 44, the storage tank and back to the pump inlet 4S, a predetermined volume of uid will flow at a predetermined low huid velocity under idling conditions. As the pump unit is speeded up, by increasing the driving energy thereto, a greater volume of iiuid will be circulated in the said circuit, resulting in'building up the pressure 'within the cylinders 43 and 43X. In this connection it will be recalled that the openings 23o: in wall 2t separating cylinders 43 and 43X cause the pressure within cylinder i3 to be transmitted to cylinder 43X. The pressure within cylinders 43 and 43x exertl forces on their respective pistons 4i and 25, operating in opposite directions and proportional to the areas of the pistons. Since the area of control piston 25 is greater than that of by- Y pass piston 4i, the piston assLmbly is caused to more rightwardly, as viewed in Figure 4, in opposition to the coil spring 28. Rightward movement of piston 4l causes a gradual closing of by-pass outlet 44 and an increase in the proportion of the fluid ow through outlet 45 as compared with the flow through by-pass outlet 44.

The pump unit of Figures l-4 is particularly designed to supply fluids undervarying volumes and pressures to iiuid motors or drives which operate under varying load conditions, such as experienced in automobile propulsion, machine tool operation and the like. Hence it is understood that the pump outlet 45 is connected to the driven uid motor (not shown) from which a leg returns to the pump inlet 4t. The increased fiow through pump outlet i5-resulting from a speeding up of the pump, in the manner described above-will cause a speeding up of the driven fluid motor. Should an increased load be placed on the driven fluid motor, or should resistance,v

be placed in the circuit leading from pump outlet 45, the pressure in cylinders 43 and 43X will rise still higher and cause a still furtherrightward movement of the piston assembly until left piston 4l nally closes the first or leftmost individual duct 42, thus shutting off the rst annular cylinder li from the pumping operation. This results in theV supplying of a smaller volume of fluid to the driven uid motor at a higher pressure, thus generating a greater torque at slower speed, as would be required to'overcome the increased load. The rightward movement of the piston assembly continues with increase in load until piston 4l passes to the right of the rst cr leftmost duct 42'in which case the iiuid discharged from the first or leftmost annular cylinder iii flows through outlet 44 and the 'oy-pass circuit, which circuit as described above does not include the driven fluid motor. Still further load increase causes further rightward movement of the piston assembly withsuccessive closing and passing of the individual ducts 42X, and 42, these ducts contributing their flow, together with the ilow from the firstduct 42, to the by-pass circuit. In the rightmost position of the piston assembly, defined by the abutting of control piston 25 with end plate 2, only the last or'rightmost duct 42XXX remains opened and included in the circuit to thedriven fluid motor. With decrease in load and resultant decrease in pressure in the inter-communicating cylinders 43 and 43X, spring 23 causes a leftward movement of the piston assembly, which causes a successive inclui sion of the ducts 42H, 42X, and finally 42 in the circuit to the driven fluid motor, thus resulting in a circulation of a larger fluid volume at a lowerpressure (which means a greater fluid velocity and motor speed).

The bleeder hole 29 in the end plate 21 has a pipe connection for a storage or accumulator tank (not shown) to remove any uid that might have trickled pastthe pistonV rings to the right of control piston 25. The purpose of the valve disc 3l, Figure 3, of by-pass piston il is to pass the fluid to the-right of the piston at such times as it coversthe openings 42, 42X, 42XX and 421XX by permitting some uid to pass through annular opening 34, as excess pressure generated inthe cylinders overcomes spring 32.

In Figure 5 is shown an embodiment of the invention, similar to that described above in connection with Figures 1-4, having a'control adapting it for Vuse as a variable speed drive or transmission. 'Ihe particular control unit illustrated particularly adapts the unit asafour speed hydraulic power converter. The right endportion of piston rod 52 is slidable within a sleeve 53, the

amasse- 4right end portion of which is provided with` ex'- ternal threads screwed into a tapped hole provided in housing 55. At its right end protruding from housing 55, threaded sleeve 53 is provided with a handwheel 56 and a lock-nut 51'. Within the bore of sleeve 53` and between the right end of piston rod 52 and` the floor of' the borev is a coiled compression of spring 54.` By means of handwheel 5e the compression of spring 54' maybe varied as desired, for a purpose soon apparent.

Fluid from*v a constant pressure source,` such as a pump, is conducted to the transmission unit shown in Figure 5, entering at inlet 6l) which leads into cylinder 43. From common cylinder 43, individual ducts 42, 42X, etc. conduct ther pressure fluid to their respective annular cylinders I'I, IIX, etc., from Which the fluid is discharged through individual passages 50 into a discharge manifold 5I which is connected by passage 58 to cylinder 43 and thence to outlet 59. A stop 6I is provided within the cylinder 43 at a point near the rst outlet duct 42 adapted to stop the leftward movement of the piston 4I so that the rst annular cylinder is at all times open to cylinder 43. In the position of piston 4I shown in Figure 5 only the rst and second ducts, 42 and 42X are to the left of piston 4I and effective to conduct the pressure fluid to their respective annular cylinders to drive the pistons thereof and deliver power at shaft I2. As the load imposed' on shaft i2 lightens, the pressure within the cylinder 43 to the left of piston 4l' decreases, permitting compression spring 54 to move the piston leftward thus cutting duct 42X off from communication with the left end or pressure end of cylinder t3. Hence the load will be carried by the single cylinder II. The reduction in capacity from two cylinders to a single cylinder reduces the volume accepted by the motor from the pressure fluid source per revolution, with the result of increasing the iiuid velocity through the niotor and the speed of rotation of the shaft. On the other hand, as the shaft load is increased, the pressure within cylinder 43 increases and causes a rightward movement of piston 4 I. against a predetermined pressure imposed on spring 54, placing more of the annular cylinders i I, etc., in communication with the pressure cylinder 43, with the result that the torque delivered to shaft i2 is increased and the speed decreased. By regulating the spring 54 by manipulation of handwheel 55 these conditions may be controlled as desired.

In the construction shown in Figures 6 to 9, the casing is formed with an upper annular portion iiI divided by webs B02 into a plurality of cylinders, these cylinders being siX in number, tix to El", respectively, in the present embodiment. Extending longitudinally and intersecting the cylinders is a piston rotor 683, provided with six pistons 62, E3, 64, 65, B6, and 61 (Figure 9). Extending in parallelism with piston rotor 653 is an abutment rotor 68 formed with a plurality of clearances one for each of the pistons. The right hand end of the upper casing section is closed by a cap 59 and the left hand end of said casing sec.- tion is open for the projection of a drive shaft 'lli which is received within the piston rotor G53, and connected for its rotation as by splines. The lower portion Blix of the casing is` preferably separable, being secured to the upper portion by cap screws 'I I.

rlhe abutment rotor 63 is provided with spindles 58X which are received within ball bearings i2. The piston rotor 603 is formed with a spindie 6IX received within a ball bearing T3, and at its left-end portion the piston rotor is received within a second. ball bearing '14..

Viewing` Figure r1 it will be seen that the lower section of casing BUI' is formed With a deep. passage at 15, and this passage will be: preferably formed in a progressive curve extending at such an angle as to bring into communication two adjacent cylinders, in this case cylinders 51X and GEX. There being six cylinders in the present ernbodiment, three of said passagesl are providedr as shown; at l5, 16,. and TI. Thus passage 15 will. af-

ford communication between. the cylinders for pistons 6T and 66;' passage 16 will afford communication between the cylinders 65X and t4x for pistons 65 and 64; and passage TI- will afford communication between cylindersY 63X and 62X for pistons 63 and 62.

The upper casing section at the lower leithand viewing Figure 6' is formed with an elongated chamber which is shown in Figure 8 which chamber has a larger cylindrical area at lil conrmunicating with an elongated cylindrical area of lesser diameter as shown at l5. Within cylinder 'E8 is a piston 39 behind which is a pre-loaded spring 8|., The piston carries a` piston rod 82, which passes through a perforated diaphrarn 53 and extends within` cylinder section l5. Piston rod S2 carries a slotted piston '84 which is similar to that shown in detail in Figure 3, Cylinder section "r9 is; provided with a Icy-pass duct' at' 85 which is adapted for communication (as: by a pipey not shown) with thev lay-pass and inlet sage 85, Figure 7. Cylinder le alsois provided with ducts at 8l, si?, and` 55 for communication respectively with cylinders 55X, 65X, 53X, according to the arrangement indicated in Figure '1.

In the operation of the device illustrated in Figures 6 to 8, which device may be described as a fluid power generator and automatic variable huid transmitter, rotation of shaft l@ by any suitable source of power will cause the abutment tol move in the direction of the arrow Figure 7, and the pistons will move through the abutment clearances in counter-clockwise dit tien. The iluid wil-l move under pressure from right to'left of the structure shown iin Fig. e and will following effect upon the automatic. vari .Jie control shown in Figure 8:

Bearing in mind that the inlet and try-pass will communicate with` an accumulator or other reservoir containing' fluid, and this in addition to its. communication with bil-pass 315, for cylinder. section 59,. and also bearing in mind 'that the inlet and by-pass Eli extends longitudinally of the casing. and is formed with openings; (such as that shown. by dotted lines at. sii, Figure 7) for communication with each of the alternate cylinders 55X, 54X and 52X, the operation of the generator in conjunction with the automatic control is governed in the following manner:

It is assumed that the unit is driven by a variable speed power supply such yas an` air motor or an internal combustion engine that may be accelerated or decelerated. The preloading spring BI is under the proper tension to retain the piston iid at a point past the by-pass opening 35 in the cylinder T9 during the idling speed of the driving un-it. As said driving unit is accelerated a pressure wil-I- be built up within the cylinders i8 and T9 and will begin to react on pistons Se and Srl so that piston 84 will successively pass the ducts 8T, 83, and 89 as the volume and pressure requirements through the discharge opening 5i demand. The discharge from said opening lli will -be employed for the propulsion of a fluid motor or other device operated by a fluid having varying volumes and pressures. It will be noted that piston 84 is a skeleton piston'having ache'clf valve 92 controlled by 'a spring 93 for the purpose of passingthe fluidV to the left of the piston at such times as it covers the openings ill, 8S, and 8g. As the pressure requirements of the load decrease, the preloaded spring will move the pistons toward the by-pass opening until the proper volume'and pressure requirements have been fullled. It will 'be noted from Figure 'l that pistons 66 and 61 are timed 180 apart and operate'as a joint unit. Piston 66 will first take in a charge of iiuid through inlet-and-by-pass 35 and duct 90, and will force a charge around its cylinder 56X through the connecting deep cylindrical passage 'land directly into cylinder 61X where it is received by piston 6l and forced around said cylinder, then discharged through duct 8'! into the cylinder 19 of the automatic control, thus completing a cycle. It will be noted that at such time as one of the pistons 66 or 61 is passing through its appropriate abutment clearance, or otherwise becomes idle, the other piston will supply the column of fluid to the automa-tic control, thus maintaining a const-ant column of the uid at all times and assuring smooth operation of the device.

I claim:

1. In a control device for a multiple cylinder pump, the combination of an elongated cylinder connected by individual ducts to the pump cylinders, a by-pass outlet at one end of the said elongated cylinder, a discharge outlet Vat the other end of the elongated cylinder, a piston slidable in the said elongated cylinder and spring pressed beyond the said by-pass outlet whereby the fluid is by-passed therethrough, said piston adapted upon increasing the power supplied to the pump to move in a direction against its said spring to close the said by-pass outlet whereby the fluid is pumped through the said discharge outlet, the said means being further adapted upon the imposition of load on the pump to move tne pistoniurther in the said direction to open the said by-pass outlet and to place successive ones of the said outlet ducts from the plurality of pump cylinders on the by-pass side or the piston and shut such cylinders from communication with the said discharge outlet whereby a smaller volume is delivered to develop a greater torque at reduced speed, said piston being of skeleton formV with peripheral openings and with its end facing the said discharge outlet of the elongated cylinder open, the said open end of the piston being in communication with the said peripheral openings, a disc slidably mounted on the piston rod and spring pressed toward the piston to close its said open end, whereby excessive pressure in the particular one of the pump cylinders the outlet of which is blocked by the said piston, will be relieved through the said peripheral piston openings and the said open end thereof.

2. The combination according to claim 1, in which the device is adapted as a fluid power generator and automatic variable fluid transmitter, and said device being provided with a plurality of pairs of annular pump cylinders, the cylinders of each pair communicating with each other and with a iiuid inlet, and one cylinder of each pair having an outlet duct, each cylinder receiving a rotary piston, and one cylinder of each pair discharging into that cylinder of the pair having the vgated cylinder of the control.

outlet duct, the outlet ductleading to the elon- 3. The combination according to claim 1, in which the device is adapted as a fluid power generator and automatic Variable nuid transmitter. the said device being provided with a plurality of pairs of annular pump cylinders, the cylinders of each pair communicating with each other and one with a fluid inlet, and one cylinder of each pair having an outlet duct, each cylinder receiving a rotary piston, the pistons of each pair of cylinders being spaced circumferentially on' the piston shaft about and the pistons of an adjacent pair of cylinders having like relative spacing but being circumferentially offset from the cylinders of the iirst Vnamed pair, one cylinder of each pair having the outlet duct leading to the control.

4. The combination according to claim 1, in which the device is adapted as a iiuid power generator and automatic variable iluid transmitter, the said device being provided with a plurality of pairs of annular pump cylinders, the cylinders of each pair communicating with each other andV with a fluid inlet, and one cylinder of each pair having an outlet duct, each cylinder receiving a rotary piston, and one cylinder of each pair discharging into that cylinder' of the pair having the outlet duct, the outlet duct leading to the elongated cylinder cf the control, the communication between the cylinders of each pair' consisting of a tubular semi-circular passageway of substantially constant cross sectional area directed in opposition to the annular cylinders, an abutment rotor intermediate the passageway and the annular cylinders, said abutment rotor being formed with clearances for the pistons and being partially encircled by the walls of said passageway.

5. In a multiple cylinder power converter, a casing provided with a plurality of annular cylinders, a shaft disposed centrally of the annular cylinders having fixed for rotation therewith a piston slidably received in each annular cylinder, a cylindrical abutment extending parallel tothe piston shaft and having openings at the annular cylinders wherein the respective pistons clear, the ter- .minal portions of each of the annular cylinders being provided with openings on each side of the abutment, a cylinder connected by individual ducts to the terminal openings on one side of the abutment, said individual ducts communicating with the last-named cylinder at openings spaced longitudinally of said cylinder, a manifold connected to the terminal openings on the other side of the abutment, a piston slidable in said lastnamed cylinder, and resilient means for resisting movement of the piston lengthwise of said cylinder in one direction, said piston being of a length suilicient to cover each of said spaced openings as it passes them in turn, said piston having a lateral opening for communication with said spaced openings and a check valve in communication with said lateral opening, and said piston being movable against said resilient means upon increased loading of the power converter by increased pressure in said last-named cylinder produced by the increased loading whereby the piston successively passes the spaced openings in said Vcylinder to automatically regulate the number of annular cylinders operating in the power cycle and thus increase the mechanical advantage through lowering the rate of Work output.

6. In a control device for a multiple annular cylinder power converter, the combination of a control cylinder connected by individual ducts to terminal openings at one end of each annular cylinder, said individual ducts communicating with the control cylinder at openings spaced longitudinally oi the control cylinder, a manifold connected to terminal openings at the other end of each annular cylinder, a piston slidable in the control cylinder, and resilient means for resisting movement of the piston lengthwise of the control cylinder, said piston being of a length suicient to cover each of said spaced openings as it passes them in turn, said piston having a lateral opening for communication with said spaced openings and a check valve in communication with said lateral opening, and said piston being movable against said resilient means upon increased loading of the power converter by increased pressure in the control cylinder produced by the increased loading whereby the piston successively passes the spaced openings in the control cylinder to automatically regulate the number of annular cylinders operating in the power cycle and thus increase the mechanical advantage through lowering the rate of work output.

7. In a control device for a multiple annular cylinder duid pump, the combination of a control cylinder connected by individual ducts to terminal openings at one end of each annular cylinder, said individual ducts communicating with the control cylinder at openings spaced longitudinally of the control cylinder, a manifold connected to terminal openings at the other end of each annular cylinder, a piston slidable in the control cylinder against resilient pressure, said piston being of a length suilcient to cover each of said spaced openings as it passes them in turn, said piston having a lateral opening for communication with said spaced openings and a check valve in communication with said lateial opening, and said piston being movable against said resilient pressure upon increased loading of the pump by increased pressure in the control cylinder produced by the increased loading whereby the piston successively passes the spaced openings in the control cylinder to regulate automatically the number of annular cylinders operating in the pump and thus increase the mechanical advantage through lowering the volume of uid delivered per revolution.

8. A control device of the character described in claim 7, in which the control cylinder has an adjoining cylinder coaxial therewith and an apertured wall separating the said two cylinders, a piston slidable in said adjoining cylinder and connected to the piston of the control cylinder, a by-pass outlet near one end of the control cylinder, a compression coil spring in the control cylinder to provide said resilient pressure, said spring holding the control cylinder piston beyond the bypass outlet when the pump is turning at idling speed whereby the uid is pumped through the by-pass outlet, said two pistons having different areas so that upon increasing the speed of the pump the pistons move in a direction against said spring to close the by-pass outlet.

9. In a control device for a multiple annular cylinder power converter, the combination of a control cylinder connected by individual ducts to terminal openings at one'end of each annular cylinder, said individual ducts communicating with the control cylinder at openings spaced longitudinally of the control cylinder, a piston slidable in the control cylinder, a manifold connected to terminal openings at the other end of each annular cylinder, said manifold connection to each cylinder remaining open irrespective of the position of said piston, and resilient means for resisting movement of the piston lengthwise of the control cylinder, said piston being of a length sufiicient to cover each of said spaced openings as it passes them in turn, said piston having a lateral opening for communication with said spaced openings and a check valve in communication with said lateral opening, and said piston being movable against said resilient means upon increased loading of the power converter by increased pressure in the control cylinder produced by the increased loading whereby the piston successively passes the spaced openings in the control cylinder to automatically regulate the number of annular cylinders operating in the power cycle and thus increase the mechanical advantage through lowering the rate of work output.

10. In a control device for a multiple annular cylinder power converter, the combination of a control cylinder connected by individual ducts t0 terminal openings at one end of each annular cylinder, said individual ducts communicating with the control cylinder at openings spaced longitudinally of the control cylinder, a manifold connected to terminal openings at the other end of each annular cylinder, a piston slidab'le in the control cylinder, and resilient means for resisting movement of the piston lengthwise of the control cylinder, said piston ybeing of a length sufficient to cover each of said spaced openings as it passes them in turn, said piston having a lateral opening for communication with said spaced openings and a check valve in communication with said lateral opening, said check valve being arranged to permit discharge from the control cylinder through said lateral opening when the piston is in positions covering said spaced openings, and said piston being movable against said resilient means upon increased loading of the power converter by increased pressure in the control cylinder produced by the increased loading whereby the piston successively passes the spaced openings in the control cylinder to automatically regulate the number of annular cylinders operating in the power cycle and thus increase the mechanical advantage through lowering the rate of work output. FRANK BERRY.

REFERENCES CITED The following references are of record in the i'lle of this patent:

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